Unit 1 The Plant Body Flashcards
What consists of the angiosperm plant body?
1) Root System
2) Shoot System
What is part of the root system?
- Structures usually belowground
- main and lateral roots and root hairs
What is part of the shoot system?
- Structures aboveground
- stems, leaves and flowers
How to identify leaves, stems and roots?
1) The external appearance and location of the organ can be used
2) The arrangement of vascular tissue varies within the three organs
3) Vascular tissue is also different in monocots and dicots
Shoot System
- Stem and leaves
- More complex than the root
- Has nodes and internodes with one or more leaves at each node
- Strands at the vascular cylinder of the stem turn outward and extend into the leaf, leaving gaps opposite the leaf
What is the function of the stem?
Supports and displays the leaves to capture sunlight
-Conduction of sugars through the phloem and water in the xylem
Growth of Stem
In length occurs by internodal elongation
-Have stomata but fewer than in leaves
What is the shoot apical meristem?
Has no protective covering, though young leaves fold over it
Primordia
Leaf–>develop into leaves
Bud–>develop into lateral shoots
What are the stem tissue systems?
1) Dermal
2) Ground
3) Vascular
Dermal
Epidermis
Ground
Cortex and pith
Vascular
Vascular bundles with phloem and xylem
Discrete vascular bundles
Vascular bundles form a single ring around the pith
Scattered vascular bundles
Scattered through the ground tissue
How do leaves vary?
Variation in leaf structure is often related to the habitat or environment
What is the function of the leaf?
Photosynthesis
How does photosynthesis works in a leaf?
A flat blade exposes a large surface area to absorb sunlight for the light reactions of photosynthesis
- Gas exchange (water and carbon dioxide) occurs through the stomates
- Veins transport (collect) the products of photosynthesis
Phyllotaxy
Pattern of leaf arrangement on the stem
Types of Phyllotaxy
1) Spiral (most common type)
2) Opposite (pairs at each node)
3) Whorled (3 or more leaves at each node)
Blade (leaf)
lamina, expanded portion
Petiole (leaf)
stalk portion
-connects the leaf to the stalk
Sessile leaf
lacks a petiole
Leaf sheath
the base of the leaf that encircles the stem; common in grasses and other monocots
Dermal Tissue System (leaf)
Leaf epidermis is usually a single layer of cells covered with a waxy cuticle with stomates embedded in this layer on the upper and lower surface
-includes hairs or trichomes
Parts of the Ground Tissue System (leaf)
1) Mesophyll
2) Palisade Parenchyma
3) Spongy Parenchyma
- for both types of parenchyma, distinction is typically not labeled with monocots
Mesophyll
Specialized cells for photosynthesis
Palisade Parenchyma
Columnar cells on the upper surface and have more chloroplasts and perform more photosynthesis
Spongy Parenchyma
Irregular cells on the lower surface, less photosynthesis
Vascular bundles
Veins are continuous with the vascular system of the stem
-Veins contain xylem and phloem
Function of the veins
Major veins–> transports photosynthesis out of the leaf
Minor veins–> collects carbohydrates from the mesophyll
Leave types
Monocot (parallel veins)
Dicot ( branching or netted veins)
Types of Leaves in the Environment
1) Mesophyte
2) Hydrophyte
3) Xerophyte
4) Sun and Shade leaves
Mesophyte
Grows in environments that are neither too wet nor too dry
-small, few air spaces
Hydrophyte
Grows submerged or requires a large supply of water
- stomata are on the upper surface
- large air spaces, help floats
Xerophyte
Adapted to arid habitats
- May have thicker cuticle and multiple layers of epidermis
- Stomata are sunken in depressions on the lower surface
- Trichomes may also retard water loss
Sun and Shade Leaves
Leaves that develop in high light are smaller in area and thicker with more layers of palisade parenchyma
